Zodiark would be correct. As noted you'd better be ready to really work - not only are they fairly recent servers, but they're also by far the least populated servers (There's about 1/4th the players on Zodiark compared to the second most populated EU server... about 1/7th the players of the most populated!). This means there's plenty of opportunity for your achievements to really matter (and I can guarantee you almost 0 competition for personal hoursing if you're so inclined) but also that high-level rare goods that might actually be somewhat common on other servers are likely going to be very challenging to get your hands on.